Molecular typing of mycobacterium tuberculosis isolates using MIRU-VNTR and ETR-VNTR methods

In spite of global epidemiological investigations on Mycobacterium tuberculosis isolates, there is insufficient data related to our country. Molecular typing methods play a key role in epidemiological studies. Although many methods were used for molecular typing, recent researches show that Mycobacterial Interspersed Repetitive Unit (MIRU)-Variable Number Tandem Repeats (VNTR) method has a high discriminatory power and reproducibility, is easy to perform, and available for multi-centric studies and automation. As is the case in the other molecular typing methods, there is insufficient data for MIRU-VNTR profile related to our country. The aim of this study was molecular typing of 152 clinical isolates which were isolated from our region, by ETR-VNTR in addition to MIRU-VNTR. The addition of ETR loci primers to MIRU loci primers allowed us to assess its effect on discriminatory power when compared to using MIRU alone.A retrospective analysis of 152 MIRU-VNTR and ETR-VNTR data was performed by a computer based program which was prepared by using QBASIC 4,5 programming language. By this program, individual and combined discriminatory powers of 15 different primers (12 MIRU and 3 ETR loci) were calculated, the clusters were differentiated and unique isolates were identified.According to the results of this study, MIRU loci 26 has the highest and MIRU loci 39 has the lowest discriminatory power. Our results indicate that the addition of these 3 ETR loci, increases the clusters 111 to 122, and discriminatory power obtained with the 12 MIRU loci. First four primers (MIRU 26, MIRU 40, MIRU 16 ve MIRU 10) which have the highest discriminatory power, remained unchanged when compared 12 MIRU with 12 MIRU and 3 ETR (Table 4-5). However, it was determined that ETR-A loci took the fifth highest place instead of MIRU 23.Beside discriminatory power, rapidity and cost-effectivity of a typing method is also considerable. As a conclusion, to get more rapid and economic epidemiological investigations and molecular typing of M. tuberculosis in case of necessity, MIRU and ETR loci primers have to be performed progressively.Key Words: Mycobacterium tuberculosis, molecular typing, MIRU-VNTR, ETR-VNTR